Improvement on constrained multi-degree reduction of Bézier surfaces using Jacobi polynomials

In this paper, we first point out that for the constrained case the result by Zhou and Wang (2009) is not optimal with respect to the L2-error. Then we present an improved method to achieve the optimal constrained multi-degree reduction using Jacobi polynomials as well, but in a slightly different way. Finally, we extend the improved method to solve another optimal constrained multi-degree reduction problem with general boundary constraints. Some examples are included to verify the improvement by our method.